Portable crimping apparatus currently in use in the industry for crimping terminals onto electrical wires are typically powered by hydraulic or compressed air actuators or electric motors of the type requiring an external power source. These hand tools necessarily require an air hose or electrical cable connecting the hand tool to a power source thereby adversely affecting the tool's convenience and utility.
One such hand tool utilizing an electric motor for crimping terminals onto wires is disclosed in U.S. Pat. No. 3,397,567 which issued Aug. 20, 1968 to Klingler. The Klingler disclosure is representative of a number of portable crimping tools utilizing electric motors or pneumatic actuators which require connection to an outside power source. Another portable crimping tool utilizing an electric motor is disclosed in U.S. Pat. No. 4,475,374 which issued Oct. 9, 1984 to Sakai et al. Of particular interest, Sakai et al. discloses a relationship of crimping force to cam lift that is substantially linear while the terminal is being deformed and then after the crimping die has bottomed out, the cam continues to lift a small amount causing the force to peak substantially higher while the apparatus deforms slightly.
None of these references is concerned with battery powered portable tools and the accompanying problem of early discharge of the battery. This can be a serious problem in field use when facilities for recharging may be limited. The present invention addresses this problem by utilizing a novel concept and structure to maintain substantially constant torque requirements for the electric motor during the complete crimping cycle thereby eliminating peak loads which contribute to early discharge of the battery. Since peak loads are eliminated, a smaller, more efficient motor may be used.